Another factor I didn't see mentioned is "mind set." For myself, it is one of the most important factors.

Last year I did my first, albeit short, tours. Prior to that I had never, not ever, rode more than 52 miles in a single day and never two days in a row. I did do a lot 25s 4 to five times a week though. First trip was 200 miles one way and my excuse was to see the grand kids. Second trip was 220 miles one way and my excuse was to see a sister I hadn't seen in years. Both times I found it was relatively easy to just keep plugging away. Longest day was 76 miles and I could have gone further. Some camping, some motel. BTW I am 68 y.o. and did it on a bike that most wouldn't consider a "touring" bike.

Go for it. Pack what you think you will need then cut it in half. Jump on your bikes and head out. You'll almost certainly have a great adventure.